Josef Myslivecek and his identical twin brother Jáchym were born to a well-to-do Bohemian miller in Prague. Both sons attended Charles University in Prague, but Josef Myslivecek dropped out in 1753 owing to his poor grades; by 1754, he and Jáchym were firmly ensconced in the family business, which Josef pursued only about the next decade, abandoning his miller's trade to become a musician. In 1763, he traveled to Venice to study composition, apparently with his brother's blessing, and scored significantly with his first attempt at opera, Semiramide, at Bergamo in 1765. By that time, Myslivecek was already known in Italy by his distinctive nickname "il Boemo" owing to the difficulty Italians found in pronouncing his true surname. His second effort in the genre, Il Bellerofonte in Naples in 1767, was a smash that established Myslivecek as one of the most popular opera composers in Italy. In 1768, Myslivecek returned on a visit to Prague in triumph, but being a true Bohemian, did not stay. His subsequent attempts to establish himself in the Viennese court came to nothing, and during a trip to Munich Myslivecek suffered a mishap during a surgical operation that cost him his nose.
Myslivecek's friendship with the Mozarts, which has helped forward his reputation considerably, began in 1770. Wolfgang Mozart made use of several thematic ideas originally put forth by Myslivecek, particularly in the opera Mitridate, rè di Ponto K. 87, which was modeled in part on Myslivecek's opera La Nitteti (1770). Mozart also seems to have absorbed some of his interest in scoring for winds from Myslivecek, who was one of the first composers to utilize winds in chamber music settings and added significant wind parts to many of his symphonies and concertos. Leopold Mozart, however, found objection to Myslivecek's use of Wolfgang's talent and influence as a stepping-stone to higher professional prominence. Wolfgang came around in 1778, when Myslivecek dropped the ball on helping cover a major commission with which he was supposed to assist for Carnival season in Naples 1779. The end was not far behind that; in 1780 a pair of operas Myslivecek composed for the Carnivals of Rome and Milan both flopped, and he died at age 43 the following February. Myslivecek was so broke that a former student paid for his funeral service.
For the better part of posterity, Myslivecek is regarded as a classical music "character" more so than as a classical musician; his alleged exploits of filial conquest among opera singers and noblewomen alike have fueled the flame of many a Gothic romance in German-speaking lands. Myslivecek himself was the subject of a saucy 1912 opera by Stanislav Suda, Il divino Boemo. The first thematic catalog of Myslivecek's work did not appear until 1999, and although it was his 25 operas that made him famous during his lifetime, his finest contributions were made to the field of oratorio, particularly in Isaaco figura del redentore (1776), such a strong work that manuscript copies of it have been attributed to both Mozart and Haydn. Myslivecek was an important figure in the development of the early symphony as well, composing more than 50 works in the genre, though several are known lost. While many Myslivecek compositions, mostly symphonies and concertos, have been revived since about 2000, the single most famous one remains the song "Ridente la calma," K. 152, a tune arranged by Wolfgang Mozart from the Myslivecek aria "Il caro mio bene," belonging to an opera yet unknown.